Cable binder application device having a concentric drive motor

ABSTRACT

A high-speed binder application device for wrapping binder material about a bundle of buffer tubes that encase a plurality of optical fibers includes a pair of opposite facing binder heads mounted on a pair of hollow shafts, each shaft being driven in rotation by a concentric drive motor mounted about the shaft. Each binder head includes a light-weight synthetic guide drum that dispenses binder material off a reel and onto the bundle of buffer tubes as it is advanced through the hollow shafts. The concentric mounting of the drive motors on the shafts eliminates shaft bending loads from drive belt tension and reduces vibrations at higher rotational speeds relative to belt-driven systems. The light weight and high strength of the synthetic guide drums allows the drums to be rotated at speeds in excess of 4000 RPM.

FIELD OF THE INVENTION

[0001] The present invention relates to manufacturing fiber optic cable,and more particularly relates to an apparatus for the application of abinder about a bundle of optical fibers.

BACKGROUND OF THE INVENTION

[0002] An increased volume of Internet use and the desire to send andreceive data-intensive multimedia applications have greatly increasedthe demands put on the existing communications infrastructure. This hasled to a push for greater bandwidth capabilities through the use offiber optic cables in lieu of traditional copper cables. Increaseddemand for fiber optic cable has resulted in a need for ever-increasingproduction rates for cable winding machines.

[0003] Fiber optic cable of various configurations are in use forcommunications. In many commonly used types of cables, the opticalfibers are encased in protective buffer tubes which are formed of aflexible plastic material. Such fiber optic cables also often include acentral reinforcing member about which the buffer tubes are arranged toprovide strength to the cable. After the buffer tubes have beenpositioned around the central reinforcing member, yarn-like binders arewound around the buffer tubes to retain the buffer tubes in positionagainst one another and the central reinforcing member. A plastic sheathor jacket is then provided over the binder and buffer tubes for addedprotection.

[0004] Various winding techniques for helically winding buffer tubesaround the central reinforcing member have been employed. Oneadvantageous method is to arrange the buffer tubes around the centralreinforcing member using a reverse oscillating lay technique. The buffertubes are provided from non-orbiting supply sources and advanced in adirection generally parallel to the central reinforcing member. One ormore lay plates are provided having a central opening for the centralreinforcing member and a plurality of radially spaced openings about thecentral reinforcing member. From the most downstream lay plate, thebuffer tubes converge towards the central reinforcing member at aclosing point and are laid against the central reinforcing member in anoscillating lay. Typically, eight turns are applied in one directionbefore reversing to the opposite direction. This technique is also knownas “S-Z” stranding in reference to the appearance of the oscillatedbuffer tubes once engaged against the central reinforcing member.

[0005] The buffer tubes and central reinforcing member are then advancedthrough an aluminum or steel binder head of a binder device where thebinder is wound around the buffer tubes. The binder device may alsoinclude a second binder head positioned downstream of the first binderhead for winding a second binder around the buffer tubes in an oppositedirection. A binder head of this type is illustrated in U.S. Pat. No.4,325,212 to Hope nee Swiecicki. As illustrated in FIG. 2, the binderhead includes a binder reel rotatably supported on a hollow shaft whichsurrounds the fiber optic cable. The shaft is supported at itsdownstream end on bearings and has an upstream free end. The shaft andthe binder reel are rotated by a conventional belt-and-pulley drive. Asthe reel is rotated, one or more binder guides pay out the binder overthe free end of the shaft so that it can be wound around the buffertubes. A capstan is typically provided downstream of the binder headsfor pulling the fiber optic cable through the apparatus.

[0006] Current cable winding machines are limited in their productionrates because the binder has to run at high speeds to get a meaningfulcable production rate. In addition, the tension in the binder as it isapplied must fall within stringent tolerances on the order of ±10%.Typically, binders are applied on the cable at a pitch, or lay length,of between 15 mm and 25 mm, most commonly 20 mm. Actual running speedsof binder application machines is currently limited to 3600 to 3800 RPM,which translates into a cable line production speed of about 76 metersper minute at a 20 mm pitch. An increase of the rotational speed of thebinder applicator to even 5000 RPM would result in a 32% cable lineproduction speed increase at the same 20 mm lay length.

[0007] It is generally difficult to achieve rotational speeds thatexceed 4000 RPM with many existing binder devices because of aconcomitant increase in centrifugal forces and vibration loads on thebinder device. Such high centrifugal forces may break or damage thebinder device. Aluminum binder heads typically weigh over 8 kg each andmay structurally fail due to centrifugal forces at a rotational speed of4000 RPM which results in a loss in cable production time.

[0008] Beyond binder head failure, the useful life of the binder devicecan be reduced by the existence of centrifugal forces, vibrations andother loads. Vibration can result from various sources includingunbalance of one or more of the drive components for the binder head, orof the binder head itself. For instance, an unbalance of one gramlocated at a 100 mm radius and rotating at 5000 RPM results in acentrifugal force of 6.24 lbs. In some existing binder devices, thevibrations of the drive components have harmonics at around 3200 to 3400RPM that coincide with the harmonics of the tubular shaft, which cancause a forced resonance of the shaft that may lead to failure of theshaft. In addition, the vibration loads and the weight of the binderhead cantilevered from the end of the shaft degrade the bearingssupporting the shaft. Tension in the pulley of the belt-and-pulley drivesystem adds to the detrimental loads on the shaft and bearings.

[0009] Therefore, it would be desirable to increase fiber optic cableproduction speeds by increasing the speed of binder application withoutdecreasing the useful life of the binder applicator or the creation of asituation where vibrations cause failure of the metal shaft of thebinder applicator.

SUMMARY OF THE INVENTION

[0010] The present invention addresses the above needs and achievesother advantages by providing a high-speed binder device for bindingtogether various components of a cable, especially a fiber optic cable,in which the binder head is driven by a concentric motor and drivesystem that does not require a cantilever mounting or belts and pulleys,thereby reducing eccentric and lateral loads on the shaft of the binderdevice. A reduction in eccentric loads on the binder device reduces theoccurrence of vibrational failure at high rotational speeds.Additionally, elimination of the conventionally used drive belt resultsin a substantial reduction in lateral loads imposed on the shaftbearings, which can increase the life of the bearings. The increasedrotational speeds allowed by the present invention can result in asubstantial increase in cable line production speeds. Increasedproduction speeds are desirable considering the increasing demand forfiber optic cable.

[0011] The high-speed binder device includes a frame supporting a hollowshaft. The hollow shaft defines a central opening through which thecable is advanced. The hollow shaft is rotatably supported by at leasttwo bearings that are spaced apart in the machine direction and mountedto the frame. A binder reel is supported on the shaft and has a supplyof binder material wound on the binder reel. A guide drum is fixed aboutthe shaft for guiding binder from the reel onto the cable. A rotarydrive is included and comprises a stator and a rotor. The stator ismounted about the shaft and is fixed to the frame, preferably at alocation between two bearings. The rotor is fixed to the rotatable shaftconcentrically thereabout so that, when the drive is energized, therotor, and hence the shaft and guide drum, are caused to rotate suchthat binder is unwound from the binder reel and wrapped around theadvancing cable. Preferably, the rotary drive comprises an electricdrive motor, the stator comprising a coil and the rotor comprisingpermanent magnets. In preferred embodiments of the present invention,the electric drive is capable of operating at variable speeds.

[0012] In one embodiment, the guide drum comprises a composite materialmade of carbon fiber that allows the drum to operate at speeds greaterthan 4,000 RPM. More particularly, the guide drum defines a tubularshape having a substantially cylindrical wall formed of compositematerial with a radial thickness of ⅛ of an inch, and has an open endand a closed end. The closed end comprises an aluminum hub to which acylindrical wall is adhered with an epoxy material. Preferably, theguide drum weighs approximately 3.6 lbs.

[0013] The present invention has several advantages. The concentricmotor and drive system reduces the eccentric loads on the shaft of thebinder device, which reduces the amplitude and incidence of damagingvibrations. A reduction in vibration loads results in an increase in thelife of the binder device and a reduction in the likelihood of shaftfailure. A smoother running binder device is also capable of achievinghigher rotational speeds without excessive wear or damage to the binderdevice.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Having thus described the invention in general terms, referencewill now be made to the accompanying drawings, which are not necessarilydrawn to scale, and wherein:

[0015]FIG. 1 is a schematic view of a high-speed binder applicationdevice according to the present invention;

[0016]FIG. 2 is a cutaway perspective view of a fiber optic cablewrapped in binder material according to the present invention;

[0017]FIG. 3 is an enlarged sectional view of the cable illustrated inFIG. 2 and taken along lines 3-3;

[0018]FIG. 4A is a partial sectional view of the first binder head andconcentric motor according to the present invention; and

[0019]FIG. 4B is a partial sectional view of the second binder head andconcentric motor according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0020] The present invention now will be described more fullyhereinafter with reference to the accompanying drawings, in whichpreferred embodiments of the invention are shown. This invention may,however, be embodied in many different forms and should not be construedas limited to the embodiments set forth herein; rather, theseembodiments are provided so that this disclosure will be thorough andcomplete, and will fully convey the scope of the invention to thoseskilled in the art. Like numbers refer to like elements throughout.

[0021] A high-speed binder device 10 according to the present inventionis illustrated in FIG. 1. The device 10 is used to manufacture fiberoptic cable 11 as shown in FIGS. 2 and 3. The individual optical fibers12 are typically formed of glass or other light-transmitting materialand thus can be quite fragile. Accordingly, one or more optical fibersare encased in several protective buffer tubes 13. The buffer tubes 13are formed of a flexible plastic material and may be color coded forease of installation.

[0022] The fiber optic cable 11 also often includes a centralreinforcing member 14 about which the buffer tubes 13 are arranged toprovide strength to the cable. At least one pair of counterrotatingyarn-like binders 15, 16 is wound around the buffer tubes 13 to retainthe buffer tubes in position against the other buffer tubes and thecentral reinforcing member 14. One preferred binder material ismultifilament untwisted polyester yarn, although other binder materialscould be used including other yarn types or tape. A plastic sheath orjacket 17 is then provided over the binders 15, 16 and buffer tubes 13for added protection. The binder device 10 could also be used to wrapcopper or other types of cable.

[0023] As described in commonly assigned U.S. Pat. No. 5,826,419,incorporated herein by reference, the central reinforcing member 14 isunwound from a supply spool (not shown) and advanced toward the device10. Several buffer tubes 13 are advanced from respective supply spools(not shown) into a spaced arrangement with the central reinforcingmember 14. The buffer tubes 13 are advanced in a direction generallyparallel to the central reinforcing member 14 and through one or morelay plates (not shown). The lay plates have a central opening for thecentral reinforcing member 14 and a plurality of radially spacedopenings for the respective buffer tubes 13. The lay plates are rotatedin a predetermined oscillating fashion about the central reinforcingmember 14. From the most downstream lay plate, the buffer tubes 13converge towards the central reinforcing member 14 at a closing pointand are laid against the central reinforcing member in an oscillatinglay so as to form a cable core structure. The cable core structure isadvanced through the high-speed binder device 10 by the pull of a mastercapstan (not shown). Additionally, an anti-rotation capstan 18 isprovided to prevent rotation of the cable core about its axis.

[0024] As shown in FIGS. 4A and 4B, the buffer tubes 13 and centralreinforcing member 14 pass through the central passage of a hollowcenter shaft 19 which is fixed to a frame 20. A first binder head 21 ismounted on a first binder shaft 22 that concentrically surrounds thecenter shaft 19. The first binder shaft 22 is rotatably driven by afirst concentric motor 23 to dispense binder 15 onto the buffer tubes 13at an upstream entrance 27 of the first shaft 22. A second binder head24 is mounted on a second binder shaft 25 concentrically surrounding thecenter shaft 19 and rotatably driven by a second concentric motor 26 todispense binder 16 onto the partially wound buffer tubes 13 as theyleave a downstream exit 28 of the second shaft 25.

[0025] The first binder head 21 has a binder reel 29 having a supply ofbinder 15 wound thereon. The first binder head 21 also includes at leasta pair of binder guides 30 which are supported on a light-weight guidedrum 31. The binder guides 30 are preferably formed of a long-wearingceramic material and include adjacent inwardly and outwardly facingguides so that the first binder 15 can be threaded in a mannerillustrated in FIG. 4A. The first binder reel 29 is supported on thefirst binder shaft 22 which is in turn rotatably supported on the frame20. The first binder shaft 22 has a downstream end 32 rotatablysupported on the frame 20 and an opposite upstream free end 33. Thedownstream supported end 32 advantageously is supported by a bearing 34,and an additional bearing 34 supports the shaft 22 at a locationintermediate the two ends 32, 33. It will be appreciated that the firstbinder 15 must be passed into the free end 33 of the binder shaft 22 sothat it may be wound under tension around the buffer tubes 13.

[0026] The second binder head 24 also includes a binder reel 35 having asupply of binder 16 wound thereon and at least a pair of binder guides36 supported on a second light-weight guide drum 37 such that the secondbinder 16 can be threaded in the manner illustrated in FIG. 4B. Thesecond binder reel 35 is supported on the second binder shaft 25 whichis, in turn, rotatably supported on the frame 20. The second bindershaft 25 has an upstream end 38 rotatably supported by a bearing 40mounted on the frame 20 and an opposite downstream free end 39. Theshaft 25 is advantageously supported by an additional bearing 40intermediate of the two ends 38, 39 of the shaft. The second binder 16is passed over a pair of pulleys 42 mounted on the second binder shaft25, extends into the space defined between the second binder shaft andthe center binder shaft 9 and extends in the direction of the firstbinder head 21. The second binder 16 then exits the space definedbetween first binder shaft 22 and the center binder shaft 9 and wrapsover the edge of the center binder shaft 9 and onto the partially woundbuffer tubes 13 entering the binder shaft. Both yarns 15 and 16 arewound onto the buffer tubes in close proximity to each other (e.g., ¼inch), but preferably do not touch. Each of the binder heads alsoincludes a brake 52 with a disc 53 and a caliper 54 for stopping therotation of the shafts 22, 25. Other brake designs could also be used,such as drum brakes.

[0027] Each of the binder heads includes a freely rotatable spool 41 onwhich the respective binder reels 29, 35 are mounted. The spools 41 aremounted concentrically about the respective binder shafts, so as to befreely rotatable on the binder shafts 22, 25 so that the binders 15, 16are easily paid off from the binder reels. Electromagnetic brakes 43 areprovided on the spools 41 for binder tension control. Preferably sensors(not shown) sense the position and speed of the spools 41. Differenttypes of sensors, such as electromagnetic or optical sensors, are commonto the art and are therefore not described in more detail herein.Because the open ends of the binder heads 21, 24 face in oppositedirections, replacement reels (not shown) can be easily advanced overthe fiber optic cable into the position in the binder head formerlyoccupied by the expended reel after the expended reel has been cut away.

[0028] The light-weight guide drums 31, 37 are comprised of a compositematerial, such as a carbon fiber material, and weigh approximately 3.6lbs as more fully described in U.S. patent application Ser. No. ______,filed concurrently herewith and which is incorporated herein byreference. The light-weight guide drums 31, 37 preferably are comprisedat least in part of a composite material having a highstrength-to-weight ratio, such as a carbon fiber material. In apreferred embodiment, each guide drum weighs approximately 3.6 lbs. Theguide drums 31, 37 have a tubular shape and are formed by asubstantially cylindrical wall 45 of lightweight material such as fibercomposite with a radial thickness of approximately ⅛ of an inch. Theguide drum has an open end 46 and a closed end 47. The closed end cancomprise an aluminum hub 48 to which the fiber composite wall 45 isadhered with an epoxy material. The aluminum hub 48 includes a flange 49which is attached to the binder shaft. The low weight of the guide drums31, 37 virtually eliminates the need for balancing of the drums. Inaddition, the cylindrical wall configuration results in an evendistribution of centrifugal forces through the guide drums 31, 37. Thehigh strength to weight ratio of the carbon fiber guide drums 31, 37allows them to be rotated at speeds in excess of 4000 RPM, and even 5000RPM, without failing.

[0029] In alternative embodiments, the guide drums 31, 37 could beconstructed of other light-weight synthetic materials such ashigh-strength plastic. The weight of the lightweight guide drum can varyand depends, in part, upon the size of the guide drum and the proportionof the guide drum constructed from the lightweight materials.Preferably, the guide drum weighs less than 4 lbs. in order tofacilitate sustained operation at rotational speeds in excess of about3800 RPM.

[0030] The first and second concentric motors 23, 26 are also suitablefor high-speed operation. Each concentric motor includes a stator 50surrounding a rotor 51 as more fully described in U.S. patentapplication Ser. No. ______, filed concurrently herewith and which isincorporated herein by reference. Each stator 50 comprises an electriccoil or coils and is fixed to the frame 20. Each rotor 51 is mountedconcentrically within its respective stator 50 and is fixed to itsrespective binder shaft 22 or 25. When the electric coils of the stators50 are energized, the rotors 51 rotate the binder shafts 22, 25.Rotating the binder shafts also rotates the guide drums 31, 37 whichunwind the binder from the binder reels 29, 35 and wrap the binders 15,16 about the advancing bundle of buffer tubes 13. The concentricmounting of each motor reduces or eliminates problems associated withbelt-driven arrangements such as large bending loads on the shafts 22,25 caused by belt tension, and the mounting of each motor between twosupporting bearings eliminates the weight of the motor beingcantilevered off of the shaft. The reduction of the loads on each shaftreduces the incidence of vibrations and makes for relatively smoothoperation, especially at speeds higher than 4000 RPM. The concentricmotors 23, 26 can be run at controlled variable rotational speeds asdesired.

[0031] The light-weight guide drum construction could be advantageouslyused in other types of binder devices. In another embodiment, a singlelight-weight guide drum and concentric motor could be used in asingle-head binder device. The single head binder device, like thedouble-head device described above, can be used for wrapping variousbinding materials including tapes about a cable wrapping tape such asMYLAR® tape or water-swellable cable wrapping tapes, or yarns of varioustypes (e.g., strength yarns, water-swellable yarns, etc.). In asingle-head binder device, the cable can pass through the center shaftin either direction. The single-head binder device can also have asupply of spare binder reels ready to replace spent binder reels asdescribed above.

[0032] The light-weight guide drum construction could also be employedin a dual head binder system that has a stranding point at the exit ofthe binder device, such as described in U.S. Pat. No. 5,826,419 toShelander et al., commonly assigned and incorporated herein byreference. This binder device includes a pair of binder heads concentricwith, and surrounding, an oscillator shaft. The oscillator shaft has aplurality of openings for receiving and guiding longitudinally advancingbuffer tubes into an oscillating lay. This allows the closing point forthe buffer tubes to be downstream of the binder heads and closelyadjacent to a locking capstan. As in the first embodiment, the binderheads are facing in opposite directions which allows for easyreplacement of spent binder reels.

[0033] In another embodiment, the stranding point is between twodual-binder devices and an anti-torsion capstan is downstream from bothof the binder devices. The first two binders are rotated together by aconcentric motor in one direction, while the second two binders aredriven by a second concentric motor in the opposite direction, toproduce a double-wrapped cable.

[0034] Many modifications and other embodiments of the invention willcome to mind to one skilled in the art to which this invention pertainshaving the benefit of the teachings presented in the foregoingdescriptions and the associated drawings. Therefore, it is to beunderstood that the invention is not to be limited to the specificembodiments disclosed and that modifications and other embodiments areintended to be included within the scope of the appended claims.Although specific terms are employed herein, they are used in a genericand descriptive sense only and not for purposes of limitation.

That which is claimed:
 1. A high-speed binder device for bindingtogether various components of a cable advancing in a machine direction,said device comprising: a frame; a hollow shaft defining a centralopening through which the cable is advanced, said hollow shaft beingrotatably supported on at least two bearings that are spaced apart inthe machine direction and mounted to said frame; a binder reel supportedon said shaft and having a supply of binder wound on the binder reel; aguide drum supported on said shaft for paying out binder from the binderreel and wrapping the binder around the cable; and a rotary drivecomprising; a stator fixed to said frame so as to surround said shaft,and a rotatably driven rotor fixed to said rotatable shaftconcentrically thereabout and within said stator so that, when saidrotary drive is operated, the shaft with the guide drum mounted thereonis caused to rotate such that binder is unwound from the binder reel andwrapped around the advancing cable.
 2. A high-speed binder device asdefined in claim 1, wherein said rotary drive comprises an electricdrive motor, the stator comprising a coil.
 3. A high-speed binder deviceas defined in claim 2, wherein the electric drive motor comprises avariable-speed motor.
 4. A high-speed binder device as defined in claim1, wherein said guide drum comprises a composite material.
 5. Ahigh-speed binder device as defined in claim 4, wherein said guide drumcomprises carbon fiber.
 6. A high-speed binder device as defined inclaim 1, wherein said rotary drive is mounted between two bearings.
 7. Ahigh-speed binder device as defined in claim 1, wherein the guide drumand the rotary drive are mounted on opposite sides of one of thebearings.
 8. A high speed binder device as defined in claim 1, whereinthe guide drum defines an upstream end and a downstream end and theguide drum is rotatably supported on said shaft at only one of saidends.
 9. A high speed binder device as defined in claim 1, furthercomprising a second hollow shaft supported by at least two additionalbearings, a second binder reel supported on the second shaft, a secondguide drum supported on the second shaft, and a second rotary drivemounted about the second shaft, the two hollow shafts being axiallyaligned end-to-end.
 10. A high-speed binder device as defined in claim9, wherein each rotary drive is mounted between two bearings.
 11. A highspeed binder device as defined in claim 10, wherein each guide drum andthe rotary drive therefor are located on opposite sides of one saidbearing.
 12. A high-speed binder device as defined in claim 1, furthercomprising a brake located between the guide drum and the rotary drive.13. A method for binding together a plurality of components of a cableat a high speed, said method comprising the steps of: advancing thecable components through a hollow rotatable shaft, the shaft supportinga binder reel having a supply of binder wound thereon; supporting aguide drum on the rotatable shaft and around the binder reel for payingout binder from the binder reel; and rotationally driving the guide drumso that the binder is wrapped around the cable components at a high rateof speed, said driving step comprising: mounting a stator having anelectric coil around the rotatable shaft, fixing a rotor to therotatable shaft concentrically thereabout, and energizing the electriccoil to cause the rotor to rotate, thereby causing the rotatable shaftand the guide drum to rotate so that binder is unwound from the binderreel and wrapped around the advancing cable components to form a cable.14. A method as defined in claim 13, wherein said driving step comprisesvarying the rotational speed of the guide drum.
 15. A method as definedin claim 13, wherein said rotationally driving step comprises drivingthe guide drum at a rotational speed of at least 4,000 rpm.
 16. A methodas defined in claim 13, wherein said rotationally driving step comprisesdriving the guide drum at a rotational speed of approximately 5,000 rpm.17. A method as defined in claim 13, wherein said rotationally drivingstep further comprises driving a guide drum comprised of a compositematerial.
 18. A method as defined in claim 17, wherein said rotationallydriving step further comprises driving a guide drum comprised of carbonfiber.
 19. A method as defined in claim 13, further comprising the stepof supporting the rotatable shaft on at least two bearings that arespaced apart.
 20. A method as defined in claim 19, wherein the statorand rotor are mounted between two bearings.
 21. A method as defined inclaim 20, wherein said step of supporting the guide drum includessupporting the guide drum on an opposite side of one of the bearingsfrom the stator and rotor.
 22. A method as defined in claim 13, whereinsaid guide drum defines an upstream end and a downstream end and saidstep of supporting the guide drum includes supporting the guide drum onsaid shaft at only one of said ends.
 23. A method as defined in claim13, further comprising the steps of advancing the cable componentsthrough a second hollow rotatable shaft, the second shaft supporting asecond binder reel having a supply of binder wound thereon, supporting asecond guide drum on the second rotatable shaft and around the secondbinder reel, and rotationally driving the second guide drum includingmounting a second stator having a second electric coil around the secondrotatable shaft, fixing a second rotor to the second rotatable shaftconcentrically thereabout, and energizing the second electric coil tocause the second rotor to rotate, thereby causing the second rotatableshaft and the second guide drum to rotate so that binder is unwound fromthe second binder reel and wrapped around the advancing cable componentsto form the cable.
 24. A method as defined in claim 23, furthercomprising the step of supporting each rotatable shaft on at least twobearings spaced apart.
 25. A method as defined in claim 24, wherein thestator and rotor are mounted between two bearings.
 26. A method asdefined in claim 25, wherein the steps of supporting the first andsecond guide drum include supporting each guide drum and the stator androtor therefor on opposite sides of one said bearing.
 27. A method asdefined in claim 13, further comprising a step of positioning a brakebetween the guide drum and the stator and rotor.